删除SQL2005一条数据

Question

表：AAA
字段值：BBB
String s=BBB;这么写怎么不对啊
"delete from UserInfo where usin_car_num="+ 's'

Answer 1

String sql = "delete from UserInfo where usin_car_num="+ "'s'"

Answer 2

String sql = "delete from UserInfo where usin_car_num='"+s+"'";

Answer 3

String sql = "delete from UserInfo where usin_car_num="+ "'s'"

Answer 4

String sql = "delete from UserInfo where usin_car_num='"+s+"'";